Summary of activities in 2023

This summary presents the technical activities performed by the Belgian National Data Centre (NDC.be) in 2023 in the context of the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The NDC.be focusses on the follow-up of the radionuclide (RN) measurements performed by the International Monitoring System (IMS) for the verification of the CTBT. Currently, 73 stations for the measurement of radioactive particulates and 26 stations for the measurement of noble gases (radioxenon) are in operation. In addition, 14 IMS radionuclide laboratories are currently in operation. For the other technologies (seismic, infrasound and hydroacoustic measurements), the NDC.be works together in a BeNeLux collaboration. 

In 2023, the NDC.be reviewed 463 RN particulate spectra to determine the relevance of the detections flagged by the International Data Centre (IDC) of the CTBT Organization. After review, most of these detections were considered as non-relevant for the CTBT verification. For the remaining detections, there was no clear indication that they could be the result of a Nuclear Explosion (NE) event. The follow-up of the noble gas samples in the IMS noble gas stations allowed the NDC.be to identify 6 samples where either an abnormally high xenon isotope detection or an abnormal xenon isotopic ratio occurred. The analysis of these 6 samples suggest that the corresponding detections are most likely resulting from the global civilian radioxenon background as no clear indication would support a NE event. During 2023, the following three specific events were investigated in more detail: i) a small but noticeable I-131 detection at the remote location of GBP67 (St. Helena, UK), ii) small but noticeable Ce-144 detections across multiple IMS stations in March 2023 and iii) artificial radionuclides detected in national monitoring systems in Northern Europe in May 2023. Next to the continuous follow-up of the radionuclide part of the IMS, technical experts of the NDC.be participated in the two Working Group B sessions of the CTBT. Additionally, the NDC.be participated in different CTBT relevant conferences, workshop and meetings. 

Beside the actual verification activities, the NDC.be is performing research to support the CTBT. One pillar of research involves atmospheric transport modelling. It includes (i) uncertainty quantification of atmospheric transport modelling, (ii) inverse modelling using the event analysis and reconstruction code FREAR, (iii) testing the use of deposition measurements for CTBT verification activities and (iv) the use of cosmogenic radionuclides measured by IMS stations to study downward vertical motion in the atmosphere. The second research pillar involves the use of porous materials for adsorption and desorption of noble gases in support of the CTBT verification.